Development of high strain-hardening lightweight engineered cementitious composites: Design and performance

This paper presents a newly developed high strain-hardening, lightweight, engineered cementitious composites, using fly ash cenospheres as the filler. That has tensile strain capacity superior to that found in other lightweight concrete materials. Test results indicate: (1) The pseudo strain-hardening indices of the new engineered cementitious composite are significantly larger than the minimum requirement specified in the literature which guarantees an ultra-high ductility. (2) Even though the increase in fly ash cenospheres content reduces the tensile and flexural strength of the high strain-hardening, lightweight, engineered cementitious composite, it has little effect on its ductility; moreover, fly ash cenospheres can significantly reduce tensile stress fluctuations and crack width. (3) A calcium silicate hydrate gel forms tightly around the fly ash cenospheres due to the pozzolanic effect of fly ash cenospheres, which increases the matrix strength and provides low density matrix to maintain high tensile, flexural and compressive properties. (4) The polyethylene (PE) fiber underwent a large extrusion deformation during extraction leaving behind a large amount of broken mortar and fly ash cenospheres fragments on the fiber surface, which gave the new composite a super high tensile strain capacity.